Sawdust drying apparatus



y 6, 1953 J. R. HECHT 2,639,911

SAWDUST DRYING APPARATUS Filed May 31 1949 3 Sheets-Sheet l l NVE NTOR (JOHN R. HECH T ATTORNEYS May 26, 1953 J. R. HECHT SAWDUST DRYING APPARATUS Filed May 31 l949 3 Sheets-Sheet '2 FNVENTOR May 26, 1953 J. R. HECHT SAWDUST DRYING APPARATUS s Sheets-Sheet 5 Filed May 31 1949 INVENTOR L/Of/V R. HECY'IT ATTORNEYS Patented May 26, 1 953 SAWDUST DRYING APPARATUS John R. Hecht, Vancouver, British Columbia, Canada Application May 31, 1949, Serial No. 96,251

6 Claims. (01. 263-36) This invention relates to apparatus for drying sawdust.

Heretofore, it has not been possible economically to dry sawdust. Sawdustis being used extensively for heating and cooking purposes, despite the fact that there is often a shortage of this product. There is usually an excessive amount of sawdust available in the summer, but because of its bulk and other difficulties in storage, a great deal of it is burned. Thus, only a relatively small quantity is kept over until the winter when the demand is greatest and, usually, the output of sawdust is the least. Sawdust, with a comparatively low moisture content, such as fir sawdust, is generally used. Large quantities of some types of sawdust, such as hemlock sawdust, are destroyed since they cannot be used because of their high water content. If sawdust can be dried economically, many more industrial uses are possible, but so far it has been economically and technically impossible to dry sawdust. The known types of driers used in dehydrating various products, such as rotary driers, cannot be successfully used with this product. One reason for this is that the sawdust must remain in contact with the hot drying gases for a relatively long time.

An object of the present invention is the provision of apparatus for drying sawdust economically so that it will require less space for storage, is less liable to deteriorate in storage, and sawdust, such as hemlock sawdust, may be used without difficulty.

, Another object is the provision of apparatus for'dryi'ng sawdust in order to provide a better product than is now available, since less of the heat created is used up in evaporating its relatively high moisture content.

Another object is the provision of apparatus by means of which the waste from a sawmill may be used for drying sawdust.

A further object is the provision of sawdust drying apparatus by means of which the moisture content of the finished product may be regulated.

Yet another object of sawdust drying'apparatus, using the waste heat from a mill', the

speed of operation of which may be regulated in accordance with the speed of operation of the mill.

' Yet another object is the provision of'saw dust drying apparatus using the waste heat of a sawmill, the speed and operation of which may be, adjusted in accordance with the quality and'species'of logs being handled by the mill. T A still further object is the provision of saw- 2 dust drying apparatus for sawmills which enables the mill to dispose of waste resulting from any species of logs, thereby enabling the mill to handle a wider variety of log species than would otherwise be the case.

An example of this invention is illustrated in the accompanying drawings, in which,

I Figure 1 is a plan view diagrammatically illustrating the sawdust drying apparatus.

Figure 2 is a side elevation, partly in section, diagrammatically illustrating the heating part of the apparatus,

Figure 3 is an enlarged section through spark arresting equipment used in this apparatus,

Figure 4 is a section taken on the line 44 of Figure 3,

Figure 5 is a longitudinal section through a drying chamber of the apparatus,

Figure 6 is a section taken on the line of Figure 5,

Figure 7 is a plan view of the drier with the top removed, and

Figure 8 is a cross section through an alternative form of drying chamber.

Referring more particularly to Figures 1 and 2 of thedrawings, I0 is an incinerator or furnace for burning waste products from a sawmill, and having a large burning section II, progressively smaller sections l2 and I3 for increasing the velocity of the gases, and a large stack l4. Waste from the sawmill is directed to an opening I! in the top of the section II of the furnace through a chute I8. eluding sawdust, is moved along the chute by an endless belt or chain [9 having scrapers 20 extending thereacross and moving along the bottom of the chute. Suitable means, not shown, is provided for operating the belt. A portion of the bottom of the chute is formed by a screen 22 which may be completely or partially closed.

or covered by a cover 23 slidably mounted on the chute.

The waste material in section I I of the furnace falls on to a grate 26 mounted therein above an ash pit 21. One or more draft doors 28 may be provided in the wall of the ash pit for controlling the draft to the grate. If desired, a blower 30 may be provided for directing air through a pipe 3| to the ash pit beneath the grate. This blower may be driven in any suitable manner, such as, by means of an electric motor 32. Air from the blower tends to lift the material up from the grate and to mix with it, thus aiding combustion.

\ A large damper or gate 35 is mounted in the The waste material, in-' 3 stack I4 and controlled in any convenient manner, such as by means of an electric motor 36. This motor is thermostatically controlled as hereinafter described.

A drying chamber 40 is provided adjacent the furnace Ill. When the screen 22 of the chute I8 is partially or completely uncovered by the plate 23, sawdust drops down on to a conveyor 42 which may transport it directly to the drying chamber or as in this example, it may transfer it to another conveyor 43 which transports it to a hopper 44 located at one end of the top of the drying chamber 40.

The sawdust is moved through the drying chamber in any convenient mamier, such as, by means of one or more endles conveyors, see Figures 5 and 6. In this example, the chamber is provided with a plurality of endless coriveycr's 48 arranged one above the other, said conveyors preferably being staggered as shown. Sawdust from the hopper 44 drops on to one end of the uppermost conveyor and is moved to the opposite end thereof where it drops down on to the adjaeent end hi the nextccnveyor which extends beyond the end of the uppermost conveyor owing to the staggered relationship of these elements. Each c'onyeyor is preferably formed of suitable perforated material, including screening, mesh or any other suitable material, so that heat can pass therethrcugh. If desired, the conveyors may bevibratd m any suitable manner, such as by Stehiid earns 19 located beneath the sawdust bearing portion of each belt.

It has been found advantageous to mount each cjonveyor on rollers 50 which ride oh tracks 5| at the opposite sides or the chamber so that each conveyor may readily be removed from or iriserte into the chamber. A large door 52 is provided at one end of the chamber in order to make possible.

The lowermost conveyorpreferably consists of a platfcrm 53 underlying all the other conveyors, and a plurality of scrapers haunted on endless chains 55 at opposite ends thereof, 'said extending across the full width of the the chamber. The platform and ere project beyond one end of the drying and are adapted to aseharge into a y 'r 51. outside said chamber. Sawdust drops act/r1 an to the inner end 6f the platform and is 'fn'oved thereal'ohg by the scrapers 5 1 into the 'conyeycr 57, said conveyor extending to a stcrag' b ts.

It is gobvio'us that the sawdust may be conveyed through the chamber by replacing the conveyor belts by ifec'iprocating screens arranged somewhat in the same way as the belts.

sawdus "may be removed from the bin 5 8 and delirere'd in bulk or in bags. However, this apparatus makes it possible to direct the, sawdust to a bri que'tting press 60. This is where it is compressed into "small units which may be easily handled and stored.

I-Idt gases from the furnace are by-passed through the drying 'eha'mber 4D. The gases from the latter chamber may be directed back to the stack M, as shown, or they may be discharged directly into the atmosphere.

I Unefway of doing this is to provide the chamber 40 with one or mere inlets and outlets B4 and 65, respectively, in we "or more or the confining walls thereof. hithi'sexample, there are several inlets st "and several outlets t5 in the same wall adjacent its top, see Figure "5. A nursery of baffles 66 project inwardly hem one wan of the chamber, while a plurality of baffles 61 project inwardly from the opposite wall thereof. Each of these bafiles extends inwardly to the edge of one of the conveyors. By referring to Figure 6, it will be seen that the baffles 66 and 61 are staggered in relation to each other so that they, along with the conveyors, form a tortuous passage which extends from the inlets back and forth between the conveyors in the chamber up to the outlets. A pipe 68 extends from the section l3 of the furnace H) to a header 69 which is connected to all the inlets 64 of the drying chamber. Another header II is connected to all the outlets B5 of the chamber and a pipe 12 leads away from said header. The pipe 12 preferably extends to the stack [4 above the damper 35. A suction fan 14 is mounted in this pipe and is driven in any convenient manner, such as by means of a motor 15. A thermostat 15a is mounted in the chamber, said thermostat being connected to the motor 36, gate 35 to control the latter in accordance with the temperature in the chamber.

Figure 8 illustrates an alternative way of directing hot gases into the drying chamber 30 and removing them therefrom. In this example. the pipe 63 is connected to the bottom of a header 16 which completely covers one wall of the chamher. The pipe 12 is connected to the top of a header 1'! which completely covers the opposite wall of the chamber. A plurality of openings II are formed in the wall of the chamber within the header l6, and a plurality of openings '19 are formed in the opposite wall of the chamber within the header 1?. Bailles 79a extend from each of the chamber walls to the adjacent edges of the conveyors 48 to form passages 19b between the latter. There is a line of openings 7'8 and 19 e'xtending the length of the chamber communicating with the ends of each of the passages 191) between the conveyors. It is preferable that the openings 18 and 19 be relatively small near the bottom of the chamber and gradually increase in size towards the top thereof, as shown.

Suitable means is provided in the pipe 63 for arresting sparks and any solid material that may be mixed with the gases coming "from the fire in the section H of the furnace. One desirable rpm at spark arrester is illustrated in F ure '3. This consists of one 'or more screens 8'0 located in the pipe, and a plurality of staggered 'baflie's 8| in said pipe. If desired, a control gate 83 may also be mounted in the pipe 6TB. Furthermore, it is desirable to provide an opening $4 in this pipe between the spark arrester and the drying chamber, said opening being controlled by a cover '85. This controlled opening provides means ahead of the header 6? for contrbllihz' the temperature in the drying chamber. carbon dioxide bottle 8'6 may be provided at this point having a tube 81 extending into the pipe 68. This carbon dioxide bottle 'is available in case. of fire in'th'e drying chamber.

In ciperauon, the waste from the mill is 'rl'l'oyed among the chute 1'8 "and any sawdust mixed with it drops thrdflgh tlie screen?! "al'nd'i's directed to the drying chamber 1'0.

furnace T0. 'The hot ases from the fire may pass up through the stack 14 or they may be partially or completely 'by passed through the pipe 38 into'the drier and back 'th'rbug h the pipe 13 to the state. This by pas's'ing is re'g'iilaited by the-dam er The meter 36 O f this damper is controlled by'the'thermestat T50. 'locatedi-n the The waste that passes the screen 22 is burned in the section ll of the chamber.

drying chamber so that the temperature therein is prevented from rising above a predetermined point. If the temperature is too high, the damper may be completely opened and all the gases pass up the stack. At the same time, to accelerate the cooling effect, the cover 85 may be opened to admit cold air directly to the The damper may be completely or partially closed so as to direct some or all of the gases through the drier.

Sawdust enters the drying chamber through the hopper 44 and is deposited on one end of the uppermost conveyor 48. The sawdust is moved back and forth through the chamber on the various conveyors until it finally drops on to the platform 53, after which the scrapers 54 move it out of the chamber on to the conveyor 51. While this is taking place, hot gases enter the chamber through the inlets 64, in the form of the invention illustrated in Figure 6, and pass back and forth between the conveyors and, to a certain extent at least, through the conveyors and sawdust, up to the outlets 65. The suction fan 14 draws the gases from the furnace through the drying chamber and directs them either directly into the air or to the stack I4 above the damper 35.

In the alternative of Figure 8., the hot gases from the pipe 68 enter the header t6 and are directed through the openings 18 into the passages 1%. From here the gases move through the openings 19 into the header 1'! and pass out through the pipe 12. By having the openings 18 relatively small adjacent the bottom of the chamber and increasing in size towards the top thereof, the hot gases are evenly distributed throughout the drying chamber.

The apparatus described above provides the operator with absolute control of the apparatus in relation to the waste of the mill, the type of product desired, and the quantity thereof required. Furthermore, it provides the operator with means for instantly putting out any fire which may start in the drying chamber. The sawdust is separated from the waste from the mill by the screen 22. The cover 23 may be used to regulate the amount directed to the drier and/or to the furnace. The temperature and quantity of gases from the burning section of the furnace may be regulated by opening or closing the draft doors 28 and/or by means of the blower. The temperature in the drier may be regulated by any or all of the following means: the suction fan 14, by opening or closing the control gate 83, by controlling the size of the opening .34 in the pipe 68, and by opening or closing the damper 35 in the smoke stack. If a fire starts in the drying chamber, carbon dioxide may be directed into it from the bottle 86. The amount of sawdust passing through the device and the moisture content thereof may be regulated by the speed at which the conveyors 48 move in the drying chamber and the number of these conveyors. If the sawdust has a high water content, a maximum number of these conveyors may be used. However, if the water content of the sawdust is relatively low, some of the conveyors may be removed from the chamber so that sawdust will remain therein a shorter time than would otherwise be the case. The spark arresting apparatus in the pipe 68 reduces or eliminates the possibility of any burning material entering the drying chamber. Thus, the apparatus may be adjusted to the speed of operation of the mill, to the species of logs being handled in the mill, to the quantity 6 of sawdust required and to the degree of moisture required in the finished product.

While the furnace described above is very suitable for use with the sawdust drying apparatus, it will be understood that any type of burner, heating apparatus, or boiler installation may be used and, therefore, the term furnace as used in the appended claims includes any of these.

What I claim as my invention is:

' 1. Sawdust drying apparatus comprising a furnace, a smoke stack connected to the furnace, a drying chamber, a pipe adapted to direct hot gases from the furnace to the chamber, a spark arrester in the pipe, a controlled opening in the pipe, a carbon dioxide bottle having a tube extending into the pipe, another pipe for removing the gases from the chamber, means for by-passing the gases through the chamber when the temperature therein is below a predetermined point, and means for conveying sawdust through the chamber to be dried therein.

2. Sawdust drying apparatus comprising a furnace, a smoke stack connected to the furnace, a drying chamber, means adapted to direct hot gases from the furnace through the chamber, a gate in the stack above the connection of the latter to the furnace, means for opening and closing the gate, means connecting the chamber to the stack above the gate, a thermostat in the chamber for controlling the gate operating means to maintain a predetermined temperature in the chamber, and means for conveying sawdust through the chamber to be dried therein.

3. Sawdust drying apparatus comprising a furnace, a smoke stack connected to the furnace, a drying chamber, means adapted to direct hot gases from the furnace to the bottom of the chamber, a gate in the stack above the connection of the latter to the furnace, means for opening and closing the gate, means connecting the top of the chamber to the stack above the gate, a thermostat in the chamber for controlling the gate operating means to maintain a predetermined temperature in the chamber, a plurality of staggered conveyors removably arranged one above the other in the chamber, a large door in a wall of the chamber to permit removal of any of the conveyors, means for operating the conveyors, means for directing sawdust on to the uppermost conveyor, each conveyor being adapted to discharge sawdust on to the one beneath, means for receiving sawdust from the lowermost conveyor, and a plurality of baiiles in the chamber for directing the hot gases between the conveyors as they flow from the bottom to the top of the chamber.

4. Sawdust drying apparatus comprising a furnace, a smoke stack connected to the furnace, a drying chamber, means adapted to direct hot gases from the furnace through the chamber, a gate in the stack, means for opening and closing the gate, a thermostat in the chamber for controlling the gate operating means to maintain a predetermined temperature in the chamber, means for removing the gases from the chamber, a chute for directing mill waste material including sawdust to the furnace, means for moving the material along the chute, a screen covered opening in the bottom of the chute, a cover for said opening, means for conveying sawdust passing through the chute screen to the drying chamber, and means for conveying the sawdust through the chamber.

5. Sawdust drying apparatus comprising a furnace, a smoke stack connected to the furnace, a

drying: chamber, a pipe adapted to direct hot gases from the furnace to the chamber, a. spark arrester in the pipe, a controlled opening in the pipe, a carbon dioxide bottle having" a.- tube extending into the pipe, another pipe for removing the gases from the chamber, means for; by-passing the gases through the chamber when the temperature therein below a predetermined point,v means for operating the hy-pass means to allow all the gases to. go up the stack when the. chamber temperature rises above. another predetermined point, a. chute ior directing mill" waste material including sawdust to the furnace, means for moving the material along: the chute. a screen covered opening in the bottom of the chute, a cover for said opening, means. for conveying sawdust passing through the chute screen to the drying chamber; and means for conveying; the sawdust through the chamber.

- 6 Sawdust drying apparatus comprising a. furnace, a smoke stack connected to theiurnace. a drying chamber, means adapted to direct hot gases; from the furnace thromghv the chamber,. a gate in. the stack abovethe connection of: the latter to the fiurnacei, means: for opening and closing the gate; means coxmecting' the chamber t0 the stack. above the gate,v a thermostat in the chamber fOl-E' control-ling the gate operating means 8-. to maintain a predetermined temperature in the chamber; a chute for directing mill waste material including sawdust to the furnace, means for moving the material along the chute, a screen covered; opening: the bottom of the chute, a cover for said opening, means for conveying sawdust passing through the chute screen to the dryim: chamber, and meansfor conveying the sawdust through the chamber.

JOHN R. HECHT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,054,765 Harris et. a1 Mar. 4, 1913 1,520,187- Lawson Dec. 3', 1924 1,524,340 Darrah Jan. 27, 1925 1,595,830" Furbush Aug. I0; 1926 l,.598;,914 Josephson Sept. '7', 1926 1,704,280 Burton Mar; 5, 1929 1 929381 Darrah Oct. 10, 1933 1,974,231 Bighouse Sept. 18', I934 2,024,316 Theissing Dec. 17', 1935 2,274,292 Hiller Fee. 24, I942 FOREIGN.- PATENTSv Number Country Date 349,583 Great Britain May 261 19-31 

